Effects of norepinephrine on the proximal tubular cells in perfused bullfrog kidney.

Abstract

Unlabelled: To study effects of norepinephrine (NE) on sodium and hydrogen ion transport, we used H(+)-, Ca2(+)-, or Na(+)-selective microelectrode and split-oil droplet techniques in doubly-perfused bullfrog proximal tubules. Peritubular membrane potential difference (EM), intracellular activities of Na+ ((Na)i) and Ca2+ ((Ca)i), and pH of the cytosol (pHi) and the lumen (pHTF) were monitored continuously during peritubular administration of NE (10(-6)-10(-7) M), phenylephrine (PHE, 10(-7) M), or dibutyryl cyclic AMP (db-cAMP, 10(-4) M).

Results: (1) The peritubular application of NE produced: a) an enhancement of proximal fluid reabsorption, b) a transient fall of pHTF by about 0.2, c) a gradual hyperpolarization of EM and a slight decrease of (Na)i with oscillation, d) a mild cell acidification by about 0.05 pH, and e) an increase of (Ca)i. (2) The peritubular perfusion of PHE (alpha 1-agonist) caused: a) a transient fall of pHTF by about 0.3, b) a transient depolarization of EM and an increase of (Na)i, followed by sustained hyperpolarization of EM and a decrease of (Na)i, c) cytosolic acidification by about 0.1 pH, and d) a slight decrease of (Ca)i, followed by a sustained increase of (Ca)i. (3) The peritubular application of db-cAMP produced: a) a reduction of proximal fluid reabsorption, b) a transient elevation of pHTF by about 0.15, c) a hyperpolarization of EM with a gradual decrease of (Na)i, d) cytosolic alkalinization by about 0.15 pH, and e) biphasic change of (Ca)i: i.e., a slight increase of (Ca)i followed by a sustained decrease of (Ca)i.(ABSTRACT TRUNCATED AT 250 WORDS)